I asked the same question a few months ago after a customer requested a tracking collar. Thanks to some help from folks here, I found out that those swivels are made be Sprenger in Germany. I contacted Sprenger directly and was directed to the US distributor. He did not stock them, but was willing to order them for me. The minimum order was a box of 50 at 9-11 dollars a piece. Here is a link to that thread. The distributor info is in the last post on there.

I asked the same question a few months ago after a customer requested a tracking collar. Thanks to some help from folks here, I found out that those swivels are made be Sprenger in Germany. I contacted Sprenger directly and was directed to the US distributor. He did not stock them, but was willing to order them for me. The minimum order was a box of 50 at 9-11 dollars a piece. Here is a link to that thread. The distributor info is in the last post on there.

I did end up making the collar for the guy. He really wanted a swivel on the collar even though there was one on the lead I made him. Not really knowing what to do I started looking for alternatives. Here is a pic of what I came up with. It was less than ideal, but the customer was happy so I guess it worked out.

That looks really nice. What weight leather did you use? I am going to attempt something similar. I may use a D-ring where the swivel is used and move the swivel to the lead. I'd love to see more pics of the collar if you have them.